Edelbrock Cylinder Heads - Killer Whale, Part 4

We Gain Half A Second And Nearlyfour Mph At The Track By Adding Edelbrock's Performer Lt1 Top Half To Our Caprice.

There comes a time in any car's buildup when you're no longer happy with bolt-ons. Although the less expensive modifications have proven to be beneficial to performance, the brick wall is finally in your face, and the next leap is a big one. Some prefer to steer away from such a move, but for those of us who can't settle for good, the next frontier generally means getting into the engine. For us, good becomes gooder with a new cylinder head and intake package.

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Edelbrock's recently introduced Performer LT1 aluminum head represents the latest in cylinder head technology. They come bare or complete with springs, valves, and rocker arm studs and offer big gains in power. The aluminum knocks about 70 pounds off any LT1's nose, and with its 2.02/1.55 valve sizing, it offers freer breathing for our stock 350-inch short-block.

When most people think of cylinder heads, they're often daunted by the huge variety of offerings for the small-block Chevy. Although it seems like a good thing at first, research will soon reveal there aren't as many options for LT1 enthusiasts because there simply aren't as many heads on the market. Many companies skipped the LT1 market and went straight for the LSX scene, but now that LT1 engines are in great abundance, several companies are now refocusing attention to the Gen II small-block introduced in 1992.

Edelbrock-which has been on an absolute tear recently with all sorts of new cylinder heads for various American V-8 applications (both popular and obscure)-recently released a line of aluminum heads for both the LT1 and high-port LT4 engines. Yes, following along in its Performer RPM line of heads, these new castings promise Gen II owners something to look forward to with respect to performance, value, and weight savings. The best part about it is that Edelbrock sells them either bare for the hardcore engine builders or as a complete assembly for guys like us who like to bolt-on and go.

Headin' OutEdelbrock's Performer LT1 aluminum cylinder heads feature many goodies that you'd expect, including generous 2.02/1.55 valves, CNC port-matched runners, and high-lift valvesprings for use with hydraulic roller camshafts. Unlike some other heads on the market, Edelbrock goes a step further and uses steel thread inserts on all the attachment points for more secure fastening. If any of you out there have ever stripped a thread in an aluminum cylinder head, then you can really appreciate this attribute.

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Looking down the intake port, you can see how Edelbrock gives each head a CNC-profiled port match. With its 170cc intake runners, the low-profile bronze valveguides ensure excellent midlift velocity for greater torque, horsepower, and more importantly, snappy throttle response for our 4,000-pound behemoth.

Also, Edelbrock's heads bolt right on without the use of any special-length fasteners or exotic valvetrain components. This keeps costs down as you take the plunge into the top-half world of more power. Available bare or complete, they're sold separately, and we went with the ready-to-run units listed under part number 61909. To install them, we picked up a set of new GM head bolts procured from the local Chevy dealer to do away with the factory torque-to-yield bolts.

To complement the heads, we decided to ditch the factory intake manifold and go with Edelbrock's matching Performer LT1 intake manifold. Aside from offering larger ports that properly match up to its heads, Edelbrock's manifold also has larger openings on the throttle body side that can accommodate 58mm throttle bores. Although our car is only equipped with a 52mm twin-bore unit (stock is 48mm), it's good to know that should we choose to upgrade in the future, the option is there for us.

It's interesting to note that a version for LT4s is also available that includes the taller port location. Edelbrock also offers LT4 cylinder heads for those who want to go beyond their '96 C4's 330hp rating.

Rounding out the installation is a set of hardened 7.3-inch pushrods and self-aligning roller rockers from Comp Cams. With its roller bearing mount and lightweight aluminum construction, the 1.5 roller rockers (part number 1015-16 for the set) will help us pick up some incremental power from reduced parasitic friction on the top half. It should be noted that it's not necessary to replace them when using the Edelbrock heads, so if you wanted to, you could reuse the stock rockers.

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Edelbrock Cylinder Heads - Killer Whale, Part 4

Edelbrock's recently introduced Performer LT1 aluminum head represents the latest in cylinder head technology. They come bare or complete with springs, valves, and rocker arm studs and offer big gains in power. The aluminum knocks about 70 pounds off any LT1's nose, and with its 2.02/1.55 valve sizing, it offers freer breathing for our stock 350-inch short-block.

Looking down the intake port, you can see how Edelbrock gives each head a CNC-profiled port match. With its 170cc intake runners, the low-profile bronze valveguides ensure excellent midlift velocity for greater torque, horsepower, and more importantly, snappy throttle response for our 4,000-pound behemoth.

Edelbrock's Performer LT1 intake is a direct replacement for the stock LT1 piece, but it offers larger 58mm throttle body openings and , of course, runners with greater cross sectional are for more airflow and power. The intake runners are port-matched right out of the box, so all we have to do is swap out the stocker.

Aftermarket roller rockers are a great way to free up parasitic frictional losses and maintain proper rocker arm geometry in performance applications. We ordered ours from Com Cams in the stock 1.5 ratio for use with the 3/8-inch rocker studs. Because LT1s use a self-aligning tip and require a narrow body to clear the valve cover bolts stands, conventional SBC rockers won't work here, so make sure you get the right ones. You'll also need a set of proper-length hardened pushrods, so go for the 7.3-inch ones like we did. It's available under part number 7949-16 for a complete set.

"Big Tom" O'Sullivan gets busy with the ratchet and starts unbolting the intake manifold. Most of the fasteners come out with a 9/16-inch-deep socket, while all the electrical items simply unplug from their respective locations. Of all the fuel-injected small-blocks we've come across, the LT1 is one of the easiest to service, especially when there's full access to it. And unlike an F-body Camaro, you're not encumbered by windshields, shock towers, or other items in Caprice that would other wise inhibit mechanical progress.

With a quick twist of the prybar, "Big Tom" pops the intake off and starts on the cylinder heads.

To access the head bolts, you'll need to undo the factory self-aligning rocker arms. They come off with a 9/16-inch-deep sockets. Since we didn't intend to reuse them, we just put everything in the trash bin. If you intend to reuse the factory rocker arms, try to keep everything numbered so that they go back into the same location.

To access the bolts that secure the alternator bracket to the passenger-side cylinder head, you'll have to undo the power steering pump first. This requires a special puller to remove the pulley and a full dreaming to the steering system. Instances like this are proof positive that professional help is the best help.

With the driver-side head off, you can take a gander at our factory hypereutectic pistons. There are four valve reliefs from the factory, so it's good to know that should we upgrade the cam for more lift, there's some room. The passenger side is more difficult to work around because of the air-conditioning system that tends to get in the way of everything.

The combustion chambers in the Edelbrock heads (right) are less shrouded than the factory castings (left) for improved breathing during low- to midlift valve events. This promotes and, of course, better cylinder filling and evacuation during part-throttle use, which helps fuel economy and emissions. Of course, the ultimate benefit that comes with increased efficiency is more power.

Working on an LT1 requires a lot of manpower. But when you run out of patience and old beer, the natives tend to get restless and take matters into their own hands. Here, the J&T crew decides to help "Big Tom" speed things up at 8 p.m.

Looking at the Edelbrock intake, you will immediately notice the plenum is raised. Unlike the factory piece, the raised design slightly increases runner length and creates an air gap under the plenum, allowing air to pass through and cool this area for more performance. It also makes it easier to cool the car down in between rounds, as you can put some ice in there.

It should be noted that LT1s use torque-to-yield head bolts from the factory. We decided to use conventional bolts, so we ordered a new set from the local dealer intended for a traditional small-block and cranked them down to 75 lb-ft each. At this point, things are starting to look pretty.

At the back of each LT1 cylinder head is a steam fitting. Because the lT1 is a reverse-cooled engine, GM used a crossover tube to collect steam that typically settles at the rear and allow it to settle back into an aqueous state when it flows back to the throttle body.

"Big Tom" uses a liberal amount of silicones gasket maker to seal the ends of the intake manifold instead of using a conventional rubber seal. This ensures a leak-free fit because it can get into every nook and cranny.

Installing the intake manifold is as simple as replacing the original one. All the sensors and fuel injectors directly transfer over and bolt right into place. We also transferred the 52mm Edelbrock throttle body, and as expected, it went on without a hitch.

After checking the rocker arm clearance, we were ready to install our valve covers back into place. Thankfully, no modifications were required to the bolt stands for the Comp Cams roller rockers to clear.

Sitting pretty, sitting proud. From our previous best of 14.405 at 92.81 mph, we were now looking at an incredible 13.903 at 96.55 mph with a 2.022 short time. That's a gain of .501 in e.t. and 3.74 mph on the top end.

See the results as we test the Edelbrock's Performer LT1 Cylinder Heads And Cam With The RPM Air-Gap Intake Manifold and see how we get a peak HP of 393.3@5700rpm, only at GM High-Tech Performance Magazine » Read More